CS252232B1 - Calcium ion selective electrode membrane - Google Patents

Abstract

Membrane for a calcium ion-selective electrode with improved selectivity coefficients, based on a neutral carrier - - substituted 4,5-dimethyl-3,6-dioxaoctanedioic acid diamide without configuration distinction at carbon atoms 4 and 5, which is achieved by the amidic nitrogen atoms of the diamide being symmetrically substituted by two phenyls and two 2-n-alkyloxyethyls, of the structural formula where R is alkyl cnH2n+1 with a P°^t of carbon atoms n= 8 to 11, such as N,N*-diphenyl-N,N"'- -di-(2-n-octyloxyethyl)-diamide of 4,5-dimethyl-3,6-dioxaoctanedioic acid or N,N'- -di-phenyl-N,N"-di-(2-n-udecyloxyethyl)-diamide of 4,5-dimethyl-3, 6-dioxaoctanedioic acid.

Description

The invention relates to a membrane for a calcium ion selective electrode with improved selective properties.

In practice, calcium ion-selective electrodes with a membrane formed by a plastic film, in which the active substance itself is suitably incorporated, are widely used.

One group of active substances used for the preparation of these membranes are the so-called neutral carriers. The preparation, use and properties of neutral carriers with an acyclic chain were described by Simon and his collaborators (D.Ammán, R.Bissing, M. Goggi, E.Pretsch, W. Simon: Helv. Čhim.Acta 58, 1 535 /1975/). Carriers based on substituted diamides of 4,4,5,5-tetramethyl-3,6-dioxaoctanedioic acid with an open chain were also described (M.Panoch, M.Semler,, O.Ryba, J.Petránek: Czechoslovak author's certificate No. 213 944) and some others with a cyclic chain. The use of neutral carriers expanded the possibilities of analytical application of the electrode by improving the selective properties.

Further improvement of the selectivity coefficients of a calcium ion-selective electrode with neutral supports based on substituted 4,5-dimethyl-3,6-dioxaoctanedioic acid diamide, without distinguishing the configuration at carbon atoms 4 and 5, will be achieved by using a neutral support according to the invention, the essence of which lies in the fact that the amidic nitrogen atoms of the diamide are symmetrically substituted with two phenyls and two 2-n-alkyloxyethyls, i.e. substances of the structural formula where R is n-alkyl, with a number of carbon atoms of 8 to 11, such as N,N'-diphenyl-N,N'-di-(2-n-octyloxyethyl)diamide of 4,5-dimethyl-3,6-dioxaoctanedioic acid or N,N'-diphenyl-N,N'-di-(2-n-undecyloxyethyl)-diamide of 4,5-dimethyl-3,6-dioxaoctanedioic acid.

Membranes with these neutral carriers exhibit a wide range of linear Nernst response to calcium ion activity, improved selectivity for calcium ions over alkali metal ions, fast response and small electrode potential drift. All of the membranes achieve a 95% slope _2 within 20 seconds when changing the calcium ion concentration, c= 10 ⁴ mol/1 to c= 10 mol/1 and a potential drift for calcium ions, c= 10 mol/1 is less than + lmV/24h.

The membrane composition, response and selectivity properties are evident from the following examples.

Example 1

A 0.2 mm thick membrane was made with a composition of 0.77 wt. % of neutral carrier, specifically N,N'-diphenyl-N,N'-di-(2-n-octyloxyethyl)-4,5-dimethyl-3,6-dioxaoctanedioic acid diamide, without distinguishing the configuration at carbon atoms 4 and 5, with the structural formula:

0.39 wt. % sodium tetraphenylborate, 60.17 wt. % o-nitrophenyl-n-octyl ether and

38.67 wt. % of high molecular weight polyvinyl chloride. An electrode with a reference electrolyte of CaCl ₂ with a concentration of 0.1 mol/1 and an internal reference argentic chloride electrode was made from the membrane. The measurement was carried out at a temperature of 239 to 295 K in a cell with a saturated kalohel electrode. The following values of the electromotive force of the cell were measured for aqueous solutions of calcium chloride:

CaCl ₂ C = mol/1 EMS in mV

IO ^-6 - 106.6

IO ^-5 - 80.1

10 ^-4 - 51.1

10~ ³ - 22.9

10 ^-2 + 3.0

10' ¹ + 28.0

By the method of separated samples using aqueous solutions of chlorides of the respective cations with a concentration of 0.1 mol/l, the following values of selectivity coefficients were determined for the electrode at a temperature of 293 to 295 K:

j = To Pot Ca, j j = Pot Ca, J NH4 3 χ 10' ⁴ Cs ⁺ 3.3 times ÍO ⁴ 1/5 x 10~ ³ Mg ²⁺ 3 times ίο ^-5 On ⁺ 5.1 χ 10' ⁴ Sr ²⁺ 5 times 10- ² To ⁺ 4 χ 10' ⁴ Ba ^{2 +} 9.7 times io ^-3 Rb ⁺ 9 x 10~ ⁴ H ⁺ 3.6 times 10 ^-2

Appendix 1 and d 2 She was made equally thick membrane as in the example 1 on the composition 0.86 wt. % neutral· his carrier like in example 1, 0.43 mass % sodium tetraphenylborate, 60.08 mass % o-nitro- of phenyl-n-dodecyl ether and 38.63 mass % high molecular weight polyvinyl chloride. Membrane was measured in same arrangement and in the same way as in example 1. Electrode response and its coefficients are as follows listed: CaCl ₂ c in mol/1 EMS in mV 10- ⁶ - 106.3 io ⁵ - 79.8 -4 10 - 50.8 io ³ - 21.9 10- ² + 4.0 10 ^-1 + 28.6 Sweat ..Sweat j = K„ Ca, 3 j = ^To Ca,j NH+ 5.1x ⁴ Cs ⁺ 5.1 times 10' ⁴ . + , «-3 2+ -5 If 4.1 times 10 Mg 2.3 times 10 On ⁺ 1.7 times 1θ' ³ Sr ^{2 +} 6.7 times 10- ² + , -3 2 + -2 To 1.2 times 10 Yes 1.5 times 10 Rb ⁺ 1.2 times "io" ³ H ⁺ 1.3 times ÍO' ²

Example 3

A membrane of the same thickness as in Example 1 was prepared with a composition of 1.23 wt. % of neutral carrier, specifically N,N'-diphenyl-N,N'-di-(2-n-undecyloxyethyl)-4,5-dimethyl-3,6-dioxaoctanedioic acid diamide, without distinguishing the configuration at carbon atoms 4 and 5, of the structural formula

0.59 wt. % sodium tetraphenylborate, 59.76 wt. % o-nitrophenyl-n-octyl ether and 38.42 wt. and high molecular weight polyvinyl chloride. The membrane was measured in the same way as in the example 1 and the measurement results are listed below: CaCl ₂ c in mol/1 EMS in mV 10- ⁶ - 107.6 10 ^-5 - 82.4 10 ⁴ - 53.4 10' ³ - 24.6 10 ^-2 + 1.3 10 ^-1 + 26.3 "Sweat" "Sweat" j = ^To Ca,j 3 = ^To Ca, j ΝΗΪ 4 4.2 x 10 ^-4 Cs ⁺ 3.2 x 10 ^-4 _If ⁺ 1.5 x 10 ^-3 Mg ²⁺ 2.9 x 10~ ⁵ On ⁺ 5.9 x ÍO ^-4 Sr ²⁺ 4.8 x 10 ^-2 To ⁺ 4.6 x ÍO ^-4 Ba ²⁺ 1.0 x 10 ^-2 Rb ⁺ 8.1 x 10 ⁴ H ⁺ 1.8 x 10 ² Example 1 d 4 A membrane of the same thickness as in example 1 was made with a composition of 1.49 wt. % neutral- of the carrier as in Example 3, 0.67 wt. % tetraphenylborate of sodium, 59.55 wt. % o-nitro- phenyl-n-dodexyl ether and 38.29 wt. % high molecular weight polyvinyl chloride. Membrane was measured same as example 1 and the measurement results are listed below: CaCl ₂ c in mol/1 EMS in mV

- 109.4

- 82.5

- 53.6

- 25.0 + 0.7 + 25.6

"Sweat" "Sweat" j = ^To Ca, j j = ^To Ca,j , .-4 + . -4 _NH4 4.9 x 10 En 4.2 x 10’ _Li + 3.5 x 10' ³ Mg ^{2 +} 4.4 x 10 ^-5 On ⁺ 1.2 x 10 ^-3 Sr ^{2 +} 4.7 x 10 ^-2 To ⁺ 7.3 x 10 ^-4 Ba ^{2 +} 1.3 x 10 ^-2 + -4 -2 Rb 7.9 x 10 H 1.1 x 10 subject INVENTION

Membrane for calcium ion selective electrode formed by a plastic film,

Claims (1)

A membrane for a calcium ion selective electrode formed by a plastic film, for example a high molecular weight polyvinyl chloride, softened with a plasticizer such as o-nitrophenyl-n-octyl ether or o-nitrophenyl-n-dodecyl ether, characterized in that the acid carrier selective for calcium ions 4,5-dimethyl-3,6-di-oxaoctanedio, without distinction of configuration on carbon atoms 4 and 5, the amide nitrogen atoms of which are symmetrically substituted by two phenyls and two 2-n-alkyloxyethyls of the structural formula wherein R is n-alkyl- ^{cn H} 2n + 1 ^with P 3 ^{-thein of} carbon atoms n = 8 to 11, such as 4,5-dimethyl-3, N, N'-diphenyl-N, N'-di- (2-n-octyloxyethyl) diamide, 4,5-Dimethyl-3,6'-dioxaoctadiic acid 6-dioxaoctanedioic acid or N, N'-diphenyl-N, N'-di- (2-n-undecyloxyethyl) diamide.